Color-image-reproducing apparatus of the image-projection type



Nov. 14, 1961 w. F. BAILEY ETAL COLOR-IMAGE-REPRODUCING APPARATUS OF THE IMAGE-PROJECTION TYPE 3 Sheets-Sheet 1 Filed April 4. 1955 Nov. 14, 1961 w. F. BAILEY ETAL COLOR-IMAGE-REPRODUCING APPARATUS OF THE IMAGE-PROJECTION TYPE 3 Sheets-Sheet 2 -Filed April 4. 1955 Nov. 14, 1961 w. F. BAILEY ETAL 3,009,015

COLOR-IMAGE-REPRODUCING APPARATUS OF THE IMAGE-PROJECTION TYPE Filed April 4. 1955 3 Sheets-Sheet 3 FlG.3b

United States Patent 3,009,015 COLOR-IMAGE-REPRODUCING APPARATUS OF THE IMAGE-PROJECTION TYPE William F. Bailey, Valley Stream, Robert P. Burr, Huntington, and Frederick C. Hallden, Floral Park, N.Y., assignors to Hazeltine Research, Inc., Chicago,-Ill., a corporation of Illinois Filed Apr. 4, 1955, Ser. No. 498,918 3 Claims. (Cl. 1785.4)

General This invention relates to color-image-reproducing apparatus of the image-projection type for color-television receivers.

In color-image-reproducing apparatus of the imageprojection type heretofore proposed, the register of the component images projected from a plurality of cathoderay tubes to a display screen has been subject to degradation caused by variations in the anode potential supplied to the cathode-ray tubes and the focus-field intensity within the tubes. Such variations may be caused, for example, by line-voltage variations affecting the anodepotential supply circuit and focus-current supply circuit of apparatus employing electromagnetic focusing or by changes or drift in component values.

In a copending application of Arthur V. Loughren, entitled Color-1mage-Reproducing Apparatus, Serial No. 471,340, filed November 26, 1954, it is proposed to reduce register degradation caused by variations of anode potential or focus current by regulating the anode potential in accordance with focus-field intensity or vice versa. While a system of this type operates satisfactorily, it may be more expensive than is desirable for some applications.

It is an object of the present invention, therefore, to provide a new and improved color-image-reproducing apparatus of the image-projection type which avoids one or more of the above-mentioned limitations of such apparatus heretofore proposed. I

It is another object of the present invention to provide a new and improved color-image-reproducing apparatus of the image-projection type in which the register of the component color images projected to the display screen is substantially independent of normal operating variations in the anode potential or focus-field intensity of the cathode-ray tubes of the apparatus.

It is another object of the present invention to provide a new and improved color-image-reproducing apparatus of the image-projection type in which the register of the projected images is substantially independent of variations of anode potential and focus-field intensity Within the cathode-ray tubes and in which the register of the projected component images can be readily adjusted.

In accordance with a particular form of the invention, in a color-television receiver including a display screen, color-image-reproducing apparatus of the image-projection type comprises a plurality of cathode-ray image-reproducing devices having individual screens for individually developing component images of a composite color image and having anode-potential output terminals and having magnetic beam-focus units which include adjustable means adjustable to provide four degrees of freedom of movement of individual ones of the aforesaid units relative to corresponding ones of the devices so that the centers of the points of impingement of the cathode-ray beams on the screens of'the devices are substantially independent of normal operating variations in anode potential and focus-field intensity within the devices. The apparatus also includes optical means for projecting the component images to the display screen and means for aligning the cathode-ray devices with respect to the optical means to project the images to the display screen in 2 focus and in register for observation as a single composite color image subject to substantially no degradation of register due to normal operating variations.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.

' Referring to the drawings:

FIG. 1 is a perspective view, partly diagrammatic, of color-image-reproducing apparatus constructed in accordance with the invention;

FIG. 2 is a side view of a cathode-ray tube and associated beam-focus and beam-deflection units employed in the FIG. 1 apparatus;

FIG. 3a is a front view of a frame support for cathoderay tube and' beam-deflection windings of the FIG. 1 apparatus;

FIG. 3b is a fragmentary side view of the FIG. 3a support taken in section along line 3b-3b of FIG. 3a, and

FIGS. 4a-4c, inclusive, are diagrams utilized in explaining the operation of the apparatus.

Description of FIG. 1 apparatus Referring now more particularly to FIG. 1 of the drawings, color-image-reproducing apparatus constructed in accordance with the invention preferably comprises a rigid frame or central box-like structure 11 of suitable metal construction. The box 11 preferably includes three faces or Walls 12, 13, 14 and an open face 15 having light-transmission apertures 16, 17, 18, 19, repectively.

The apparatus 10 includes a plurality of cathode-ray image-reproducing tubes 62, 61, 60 preferably having spherical tube faces coated With phosphor screens for individually developing component images, for example, red, green, and blue images, respectively, and individually mounted on rigid frames 27, 28, '29 attached to the outer surfaces 12, 13, 14 of the box 11. The frames 27, 28, '29 are diagrammatically represented in broken-line construction in FIG. 1 and preferably are constructed in a unitary structure with the box 11.

The projector 10 also includes optical means for projecting the component images to the display screen. For example, considering for the moment frame 29, there preferably is attached to that frame a light-condensing spherical mirror 30 rigidly disposed opposite the face of the cathode-ray tube 60. The optical means preferably also includes a plane mirror 32 having an aperture 3'3 therein for insertion in the cathode-ray tube 60 and fixedly disposed at approximately a 45 angle with respect to the axis of the cathode-ray tube.

The optical means also preferably includes an aspherical lens 34 of conventional type fixedly disposed in the lighttransmission aperture 18 for projecting the component image developed by tube 60 to a pair of dichroic crossedplane mirrors 20, 21 diagonally and rigidly disposed within the support 11. The mirror 20 may, for example, comprise a red and green light-transmissive and blue light-reflective mirror while the mirror 21 may, for example, be a blue and green light-transmissive and red light-reflective mirror. The mirrors 20, 21 are effective to translate and reflect the light incidentthereon through the open face 15 of the box 11 to a plane mirror 35 suitably disposed with respect to the apparatus 10 for reflecting component color images projected by the apparatus to a display screen 36 having suitable light-trans mission properties. 1

Referring now more particularly to FIG. 2. of the drawings, there is represented a side view of-the cathode-ray tube 60 and its associated beam-focus unit 55 and deflection winding structure 54. The'deflection winding 3 structure 54 is rigidly attached to a suitable mounting plate 56.

A beam-focus unit 55, represented as being of the electromagnetic type but which may alternatively be of the permanent magnet type, is bolted to the mounting plate 56 by means of suitable screws through a flange 57, end plate 57a, adjustable auxiliary magnetic pole piece 57b for adjusting the focus-field distribution in the unit 55, and a ring spacer 58. The unit 55 houses a suitable beam-focus winding (not shown). The cathode-ray tube 60 is supported at the gun end thereof by a suitable clamp 51 attached to the focus unit 55 and the bulb of the tube is firmly supported within structure 54 by suitable means (not shown). An anode-potential input terminal 70 is connected to a suitable coating within the cathode-ray tube which serves as the high-voltage anode thereof. As more fully explained subsequently, the beamfocus unit 55 including its associated magnetic pole piece 57b is so disposed with respect to the cathode-ray tube 60 that the point of impingement of the cathode-ray beam on the screen of the tube is substantially independent of variations in the anode potential or focus-field intensity within the tube. The tubes 62 and 61 of FIG. 1 and their associated beam-focus and deflection windings are similar in construction to the tube 60 and its associated focus unit and deflection winding.

Referring now more particularly to FIGS. 3a and 3b, the portion of the frame 29 which supports the picture tube and focus unit is represented in detail. The frame 29 has a section 71 which preferably is unitary with the box 11 of FIG. 1. An annular support 72, shown in fragmentary view, is bolted to the section 71 by suitable screws 73a, 73b, 730 through oversize holes in the support 72 as represented in broken line. A fourth screw (not shown) passes through oversize hole 79a in support 72 and hole 79b in frame section 71. A screw 74 threaded in the support 72 and bearing against a flange of frame section 71 may be employed in cooperation with spring mounts 80, 80 to adjust the position of the support 72 along the axis of the screw 74 by loosening the screws 73a-73c, inclusive, and that through hole 790. A similar screw 74a threaded in the support 72 and bearing against a flange of frame section 71 may be employed in cooperation with spring mounts 80a, 80a to adjust the position of support 72 along the axis of screw 74a in a similar manner.

There is also provided an inner semiannular support 75 having a flange 75b and projecting sleeves 79 and 81. The mounting plate 56 of FIG. 2 may be rigidly attached to support 75 by fastening the plate 56 of FIG. 2 under screwheads 79c, 79d, 79e of FIG. 3a onto a suitable surface plane 75a thereby mounting the beam-focus unit, deflection windings, and cathode-ray tube. The support 75 is rotatably disposed with respect to the ring 72 by means of adjustable screws 76, 77, 78 in cooperation with springs 96, 97 and 98, 99, only partly apparent in FIG. 3a.

Referring now more particularly to FIG. 3b, the screw 76 is threaded through sleeve 79 of the support 75 and bears against surface 81 of the support 72. Suitable socket means (not shown) may be employed to assure accurate, stable location of the screw'on the surface 81, Screw 78 (not shown in FIG. 3b) is mounted in a similar manner while screw 77 is threaded through a flange 72a of support 72 and bears against flange 75b of support 75. Each of the screws 76, 77, 78 rocks the inner support 75 and attached beam-focus unit, cathode-ray tube, and deflection windings about an axis passing through the pivot points of the other two screws. The frame 29 and its counterparts, frames 27 and 28, serve, therefore, as means for aligning the cathode-ray tubes with respect to the optical means to project the component images to the display screen in focus and in register for observation as a single composite color image subject to substantially no deg-. radation of register due to normal operating variations of the anode potential or focus-field intensity within the tubes. More particularly, means for adjusting the cathode-ray tubes and the beam-focus units, with the faces of the cathode-ray tubes displaceable about the centers of curvature of the faces to maintain the images in focus as projected to the display screen, while providing a register adjustment, comprises the support 75, screws 76, 77, 78 and associated springs, and similar elements in frames 27 and 28 of FIG. 1, as will be more fully explained subsequently. In this connection, the pivot ends of screws 76 and 78 define a line intersecting the optical axis of the optical system associated with frame 29 at the point at which the center of curvature of the picture tube screen should lie.

Operation of FIG. 1 apparatus Considering now the operation of the FIG. 1 apparatus, the individual beam-focus units should first be so adjusted with respect to the cathode-ray tubes that the centers of the points of impingement of the cathode-ray beams on the tube screens are substantially independent of variations in the anode potential or focus-field intensity within the tubes. This may be accomplished by applying anode potential and focus current to a given cathode-ray tube and focus winding without applying line-scan and field-scan signals to the associated deflection winding so that an undeflected light spot is formed by the cathoderay beam on the face of the tube.

The anode potential or the focus current may then be varied. It will ordinarily be found that the light spot on the tube face moves in response to such variation of the electricor magnetic-field intensity. The magnetic pole piece 57b of beam-focus unit 55 of FIG. 2 may then be repositioned with respect to the cathode-ray tube 60, causing the light spot to move to a different position on the face of the tube.

By adjusting the position of the pole piece 57b of the focus unit with respect to the cathode-ray tube, it will be found that for a given focus current or high-voltage variation the spot displacement decreases in response to adjustment in one direction and increases in response to adjustment in other directions. By adjusting the position of the pole piece 57bwith respect to the cathoderay tube so that the spot displacement decreases, a position of adjustment can be reached where the cathode-ray beam position on the tube face does not change and thus is independent of normal operating variations in the anode potential or focus-field intensity.

Theoretically, if the electron gun shoots the cathoderay beam to the center of the tube face along the axis of the effective magnetic lens formed by the focus field and if the focus field is uniformly distributed, the displacement of the light spot on the tube face will be 'insen sitive to variations in the electricor magnetic-field intensity within the tube. However, in practice it has been found that the position of zero displacement of the light spot may occur awayfrom the center of the tube face because the electron gun axis does not ordinarily pass precisely through the center of the tube face and because the position of the focus-unit body may be misaligned initially.

We have found that with four degrees of freedom controlling the focus-field location relative to the electron beam, for example, lateral displacements of the focus field in two perpendicular directions in a plane essentially at right angles to the tube axis and tilting the focus field about two perpendicular axes in the above mentioned plane, the location of the spot for zero displacement in response to voltage variations may be made to occur over a wide range of positions on the face of the tube. Some of these positions are near the center of the tube face. i

The four degrees of freedom are provided in the FIG. 2 apparatus by lateral displacements of the body of the focus unit 55 and by displacements of the pole piece 57b and by tilting of the tube neck within the focus field. By

a proper combination of these adjustments, tilting and lateral displacements of the lens may be accomplished. Accordingly, if after a first adjustment of the magnetic pole piece 57b the position of the spot for zero displacement does not occur near the center of the tube face, the body of the focus unit 55 may be shifted relative to the tube and the magnetic pole piece may then be readjusted to cause the position of the spot for zero displacement to occur near the center of the tube face.

When the three cathode-ray tubes and associated beamfocus units have been adjusted in the foregoing manner, the tubes and associated units may be bolted to the frame sections 27, 28, 29' of FIG. 1. Line-scan and fieldscan deflection voltages may then be applied to the linescan and field-scan windings associated with the tubes to develop image rasters. A suitable video signal may also be applied to the input terminals of the tubes so that the tuba may be readily aligned to project images to the display screen in focus and in register as a single composite color image which is subject to substantially no degradation of register under normal operating variations of the electricor magnetic-field intensity.

The adjustment of register of the three cathode-ray tubes may be understood by considering the positioning of the cathode-ray tube 60 accomplished on the support 29 with reference to FIG. 4a. The image raster on the tube face will be in focus on the display screen 36 of FIG. 1 when the spherical tube face lies along an imaginary focal surface, represented by broken line 93, having the same center of curvature 94 as the tube face when properly positioned and the spherical mirror 30. It may be found, however, upon initially inserting the tube in the unit 29 that the tube face assumes a position represented in FIG. 4a in broken-line construction. Then, by loosening screws 73a73c of unit 29 and adjusting screws 74 and 74a, the position of the tube may be altered to that represented in FIG. 4b. By adjusting screws 76, 77, and 78, if necessary, the tube may be positioned as indicated in FIG. 40 with its face in the focal surface. Then, by adjusting screw 78, the face of the tube may be moved in the focal surface in a first direction and, by differentially adjusting screws 76 and 77, the face of the tube may be moved in the focal surface in a direction normal to the first direction on the spherical surface. Accordingly, by adjusting the screws 76, 77, 78, with repetition of adjustment if necessary, the raster on the face of the tube may be registered with the rasters of the other tubes as projected to the display screen while maintaining the optical focus of the projected images since an image anywhere on the focal surface is projected in focus to the display screen.

From the foregoing description it will be apparent that color-image-reproducing apparatus of the image-projection type, constructed in accordance with the invention, has the advantage that the image register is substantially independent of variations of the anode potential or focusfield intensity encountered under normal operating conditions. The apparatus has the further advantage that circuits associated therewith are less complex and costly than those previously employed because a high degree of regulation of the anode potential or focus-field intensity is rendered unnecessary.

While there has been described what is at present considered to be the preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. In a color-television receiver including a display screen, color-image-reproducing apparatus of the imageprojection type comprising: a plurality of cathode-ray image-reproducing devices having individual screens for individually developing component images of a composite color image and having anode-potential input terminals and having magnetic beam-focus units which include adjustable means adjustable to provide four degrees of freedom of movement of individual ones of said units relative to corresponding ones of said devices so that the centers of the points of impingement of the cathode-ray beams on said screens of said devices are substantially independent of normal operating variations in the anode potential and focus-field intensity within said devices; optical means for projecting said component images to the display screen; and means for aligning said cathode-ray devices with respect to said optical means to project said images to the display screen in focus and in register for observation as a single composite color image subject to substantially no degradation of register due to normal operatin g variations.

2. In a color-television receiver includ ng a display screen, color-image-reproducing apparatus of the imageprojection type comprising: a plurality of cathode-ray image-reproducing devices having individual phosphor screens for individually developing component images of a composite color image and having electrical potential input terminals and having magnetic beam-focus units, said units including means adjustable to provide for the rotation of said units about two mutually perpendicular axes which are both perpendicular to the axis of the device thereof and further including means adjustable to provide translation of said units along said two mutually perpendicular axes, so that the centers of the points of impingement of the cathode-ray beams on said screens of said devices are substantially independent of normal operating variations in the electricand magnetic-field intensity within said devices; optical means for projecting said component images to the display screen; and means for aligning said cathode-ray devices with respect to said optical means to project said images to the display screen in focus and' in register for observation as a single composite color image subject to substantially no degradation of register due to normal operating variations.

3. In a color-television receiver including a display screen, color-image-reproducing apparatus of the projection type comprising: three cathode-ray tubes having spherical faces for individually developing component images of three different colors and having anode-potential supply terminals and having magnetic beam-focus units which include adjustable means adjustable to provide four degrees of freedom of movement of individual ones of said units relative to corresponding ones of said tubes so that the centers of the points of impingement of the cathode-ray beams on the tube faces are substantially independent of normal operating variations in the anode potential and focus-field intensity within the tubes and that said developed images are substantially centered on said tube faces; optical means including spherical mirrors dis posed opposite the faces of said cathode-ray tubes and including aspherical correction lenses for projecting said images to the display screen; and means for adjusting said cathode-ray tubes and beam-focus units with said faces of said cathode-ray tubes displaceable about the centers of curvature of said faces to maintain said images in focus as projected to the display screen while providing a register adjustment to provide a single composite color image subject to substantially no degradation of register due to normal operating variations.

Epstein Apr. 17, 1951 Hoellerich Sept. 18, 1951 

